The present invention relates to a process for producing an aluminum alloy sheet of predetermined final gauge. In particular, the process can be used to provide an aluminum alloy sheet which can be employed as a can stock.
A variety of aluminum alloys are known within the art. These alloys include 3000 series (aluminum-magnesium-manganese), and 5000 series (aluminum-magnesium).
In the past, a conventional sheet for can body stock has comprised an aluminum alloy from the 3000 series, in particular, alloy having the Aluminum Association designation AA3004. This stock is an aluminum-manganese alloy which has been produced from conventionally direct-chill-cast ingot up to 24 inches thick by scalping and homogenizing the ingot, and successively hot rolling and cold rolling to the desired final gauge. In addition, an anneal treatment step is often employed between the hot and cold rolling operations, with the annealing gauge so selected so that the amount of cold reduction to final gauge after annealing is about 85 percent, to thereby provide can body stock and H19 (extra hard) temper. This practice imparts the combination of properties currently required for commercial body stock.
However, because the 3004 alloy has relatively low strength and ductility, its use as a can top end, and other similar applications, is greatly limited. Furthermore, because these alloys belong to the aluminum-manganese series, they have largely been considered to be un-heat treatable when compared to, for example, the Al--Mg--Si, Al--Cu--Mg, and Al--Zn--Mg series.
Even in those instances when certain 3004 alloys have been "heat treated", see, for example, U.S. Pat. No. 3,787,248 to Setzer et al., the conditions have been carefully controlled. Moreover, an alloy such as that disclosed in Setzer cannot be effectively employed as can tops and similar applications.
Accordingly, the need still exists for a process for providing a can stock from an alloy such as AA3004 which can stock has improved strength and ductility.
It is an object of the present invention to provide a process for the heat treatment of aluminum alloys, particularly un-heat treatable aluminum alloys such as AA3004.
These and further objects will become apparent from this specification and claims which follow.